An empirical relationship for predicting the surface settlement due to EPB-TBM excavation – Case study: Mashhad metro line 2

Abstract

Surface settlement close to sensitive structures is a challenging issue in civil and geotechnical engineering. In this study, 3D simulation of TBM excavation has been implemented with the FLAC3D code and then the results compared with real monitoring data. Sensitivity analysis was performed to find out all influencing factors on the surface settlement, such as the tail void grouting pressure (Pt), the face pressure (Pf), the tunnel diameter (D), overburden (q), shield thickness (t), and the length of the shield (L). The results show that the face pressure, tail void grouting, and tunnel diameter have a considerable effect on the maximum ground displacement. In this paper, the monitoring data from Mashhad Metro was used to verify the numerical simulation. Data monitoring for about 47 sections between A2 and D2 stations was selected and a multiple regression analysis was performed. Based on linear regression, an empirical relationship was obtained, that its coefficients confirmed the sensitivity analysis results.